1. Field of the Invention
The present invention generally relates to a head module for a spacer ink, an ink feeding module and a spacer-forming apparatus having them incorporated therein.
2. Discussion of the Related Art
As a method for arranging a spacer on a substrate at predetermined positions to uniformly keep cell gaps between a color filter substrate and an array substrate of a liquid crystal display, there has been heretofore proposed a method for printing an ink having the spacer dispersed therein on the substrate by using a printing apparatus.
For the printing apparatus, an ink jet-type printer in which the ink is jetted out on printing positions through nozzles is generally used. If the spacer is not uniformly dispersed in the ink, discharging ink from the nozzle is not stabilized and problems occur (such as, discharging disorder, anomaly of discharging speed and/or direction, and instability of the number of spacers in drops of the ink liquid jetted from the nozzle).
For example, JP11-7028A describes a printer wherein a cooler and a piezoelectric element-based ultrasonic generator are provided for a stirring tank in which a spacer-containing solution is placed, the spacer-containing solution is stirred and dispersed inside the stirring tank with ultrasonic waves without rise in temperature, and the spacer is discharged. However, there is a problem in that the spacer sediments settle in the pipelines between the stirring tank and heads, head ink chambers, etc.
Although JP2002-72218A describes a printing apparatus in which an ink inside an ink chamber of a head can be circulated, there is another problem in that a head nozzle plate can become clogged with foreign matters mixed into the ink. Further, as the printing apparatuses have recently become larger, the ink feeding lines from ink bottles to head modules become longer so that settlement and aggregation of spacer inside the ink feeding lines cause various problems. The above-mentioned related art is disclosed in Japanese Patent Laid-Open Publication No. H11-7028, No. 2002-72218, No. 2002-277622 and No. JP2003-275659.